Aluminum alloys are used in aerospace and space applications because of their high strength, high ductility, high fracture toughness and low density. However, aluminum alloys are typically limited to use below about 250° F. (121° C.) because above that temperature most aluminum alloys lose their strength due to rapid coarsening of strengthening precipitates therein.
Considerable effort has been made to increase the temperature capability of aluminum alloys. Some attempts have included using aluminum-iron and aluminum-chromium based alloys, such as Al—Fe—Ce, Al—Fe—V—Si, Al—Fe—Ce—W, and Al—Cr—Zr—Mn, that contain incoherent dispersoids. However, the strength of these alloys degrades at higher temperatures due to coarsening of the incoherent dispersoids. Furthermore, these alloys have lower ductility and fracture toughness than other commercially available aluminum alloys.
Other attempts have included using aluminum alloys such as Al—Mg and Al—Ti that are strengthened by incoherent oxide particles. While these alloys have promising strength at high temperatures, they have lower ductility and fracture toughness than other commercially available aluminum alloys.
Yet other attempts have included using Al—Sc based alloys that contain low volume fractions of strengthening coherent dispersoids. However, since these Al—Sc based alloys were developed to obtain improved superplasticity (which requires lower flow stress at high temperatures), they are not suitable for providing high temperature strength (which would require much higher flow stress at high temperatures) at temperatures up to about 650° F. (343° C.).
Still other attempts have included using Al—Sc based alloys that contain gadolinium and/or zirconium, and preferably magnesium too. While these alloys have good ductility and fracture toughness, they are only useful at temperatures up to about 573° F. (300° C.).
Existing aluminum alloys lack the desired strength, ductility and fracture toughness that are needed for many applications at temperatures up to about 650° F. (343° C.). Therefore, it would be desirable to have aluminum alloys that have the desired strength, ductility and fracture toughness that are needed for various applications at temperatures from about −420° F. (−251° C.) up to about 650° F. (343° C.).